Water
28 APPLICATION OF THE LAWS OF HYDRAULICS
Assume that a bell glass with an orifice of an area w, within
which the kerosene is con-
stantly maintained at a
height PI (Fig. 22), is im-
mersed in water. Neglect-
ing, for the moment, the
coefficients of contraction /q
and of velocity /C2, which, for
this case, have not been de-
termined, the formula for
the flow will be simplified.
The hydrostatic pressure at
the orifice co will be equal
F 2r> "k° ^ne weight of a column of
water H less the weight of
a column of kerosene of the same height, that is to say:
8 = H (Awater — Aj
A designates the specific weights corresponding to the indices.
But as this head must be given in meters of height of the liquid
which is flowing, the expression for the head will be
r —A;
^kerosene — *
kerosene
Aker<
Introducing this value of h in the formula for the volume
flowing, will give, for the volume of a light liquid (kerosene)
flowing through an orifice into a heavy liquid (water), the following
expression:
AWater —2
(A)
Passing to the case of the air and the gases in furnaces, this
expression will become
Q =
r — Ag
Agas
in which H designates the distance from the lower free surface
of the gas to the opening in the roof, or, as it may be said, the
thickness of the layer of gas.